Capturing Precession

Star Axis -- which looks like an immense granite-and-concrete arrowhead -- is in part an instrument for capturing "precession," which is the gigantic ellipse made by the star Polaris. For centuries, mariners have set their course by Polaris, so named because of its proximity to the North Pole. But because of changes in the tilt of the Earth’s axis, from our terrestrial perspective, Polaris is far from fixed; rather, it travels in a great ellipse over the course of 26,000 years before realigning itself with the northernmost point on the planet. Like a cosmic caliper, Star Axis reveals Polaris’s relative alignment.